(1) Field of the Invention
This invention relates generally to camera modules and relates more specifically to movable lens barrels being moved using ball bearings and a detection system of heavy mechanic shock as e.g. if the device holding the camera module drops to ground.
(2) Description of the Prior Art
Digital camera modules are used with many electronic devices such as e.g. mobile phones, personal data assistants (PDAs), computers, etc. These camera modules have to be as small as possible, reliable, and easy to be used, robust and require minimal power consumption. Furthermore the design of the camera modules should allow low manufacturing cost, while the quality of the images has to conform to a high standard.
Therefore modern camera modules should allow auto-focusing and minimal friction of the bearing for a movable lens barrel in order to achieve precise focusing of the camera.
It is desired that after a heavy mechanic shock a movable lens should be re-initialized without manual intervention to be able to continue to operate the camera module right away after the shock.
There are known patents dealing with the design of camera modules.
U.S. patent Publication (US 2008/0075446 to Utz) teaches a horological motor of the Lavet motor concept is used to form an actuator to control movement of a lens system to reduce power consumption in digital camera units used in various electronic equipment, e.g. PDA's, mobile phones, digital still cameras and camcorders, and as a result increase battery life. The coils of the horological motor are driven with CMOS I/O signals eliminating the need for high current motor drivers and allowing the integration of all picture capture functions, including the light sensitive pixel array, into a single chip to form a system on chip implementation. A plurality of actuators is used to control a lens system comprising auto focus, zoom and shutter and iris functions. A gear transmission system is used to allow the motor of the actuator to move in micro step, which allows calibration of the motor against mechanical barriers. When an environmental event resulting to a shock force to be imparted upon the gear system of the digital camera unit, the teeth of the gear system become disengaged allowing the gears of the digital camera unit to be freed of mechanical constraint and allow the gear system to be neutral to any mechanical force imposed between the optical elements and the horological motor. Under this condition the lens packets may move and loose their current position; therefore, a calibration cycle is used after such a shock condition. The calibration is performed by moving the lens packets to known end positions, designed as mechanical stops, and then the lens packets are moved in a controlled manner back to the position prior to the shock event or by the demand of the user.
U.S. patent (U.S. Pat. No. 7,408,586 to Ueda et al.) discloses a digital camera of the present invention including a microcomputer having a live view mode controlling so that image data generated by a CMOS sensor or image data obtained by subjecting the image data generated by the CMOS sensor to predetermined processing is displayed on a liquid crystal monitor as a moving image in real time, wherein the microcomputer controls so that, when the live view mode is set, the digital camera comes out of the live view mode, and setting information on the digital camera is displayed on the liquid crystal monitor, in accordance with the manipulation of the manipulation portion. Due to this configuration, in a digital camera that includes a movable mirror and is capable of displaying a subject image in a live view through an electronic viewfinder, the operability thereof can be enhanced. A gyrosensor measures an angular speed continuously. The CPU integrates the angular speed measured by the gyrosensor to obtain an angle. The CPU uses the obtained angle for controlling hand shaking correction in the hand shaking correction unit, and monitors a change amount per predetermined time of the obtained angle. Then, when the change amount reaches a predetermined value or larger, the CPU notifies the microcomputer that the change amount reaches a predetermined value or larger. Upon receiving this notification, the microcomputer determines that a shock has been applied to the camera.
U.S. patent (U.S. Pat. No. 7,333,723 to Sato) describes a camera comprising a sensor array wherein multiple pixels are arrayed in the base-length direction, a focusing unit for performing focusing of the camera based on the image output from the sensor array, a first detection unit for detecting the movement of the image signals in the base-length direction, a second detection unit for detecting the change in a predetermined pixel signal of the image signals over time, and a movement detection unit for performing movement detection based on the output from the first and second detection units. A CPU within the camera makes judgment with regard to the output from the acceleration sensor (accelerometer IC) in a judgment processing. Thus, even in the event that the camera receives shock due to the barrier being opened, or due to the camera being held by the user, a warning display regarding holding is prohibited for a predetermined time period in the processing of following steps.